(CNN) -- More than 200 Saudi and foreign militants have been arrested over their alleged involvement in various plots, including assassinations and a planned attack on an oil facility, Saudi officials say.

Militants were alleged to have plotted an attack on an oil facility such as this one in the Eastern Province.

The arrests took place over the past few months but were kept secret so as not to jeopardize ongoing investigations, a Ministry of the Interior official said Wednesday.

Eight of those being held are accused of involvement in a plot to attack an oil facility in the Eastern Province, where much of the nation's oil industry is based, and had set a date for the attack.

Another militant cell is alleged to have planned to assassinate Saudi religious figures and security officials, while a separate cell allegedly planned to smuggle eight shoulder-fired rockets into the kingdom from Yemen for terrorist operations.

The official said 112 of those arrested were "linked in with elements stationed abroad who facilitate the exit and travel of those to conflict zones" such as Iraq.

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U.S. military officials have said that Saudis make up the largest contingent of foreign fighters in Iraq, while a Saudi counterterrorism official noted that fighters returning from Iraq to Saudi Arabia represent a "troubling" phenomenon.

Thirty-two individuals -- Saudis and non-Saudis -- were arrested for allegedly providing financial support to other militants; 16 others were arrested for alleged involvement in the publication of a militant newsletter called Sada Alrafidain.

According to the Saudi counter-terrorism official, the number of arrests is the largest ever announced by the ministry.

The Saudi official said the Saudi government released the information before the Hajj pilgrimage season, when 2 million pilgrims travel to the holy sites of Mecca and Medina, in order "to alert the public of the ongoing threat to security in the kingdom." E-mail to a friend